added references on torsion D-brane charge:

Volker Braun,

*K-Theory Torsion*[arXiv:hep-th/0005103]Ilka Brunner, Jacques Distler,

*Torsion D-Branes in Nongeometrical Phases*, Adv. Theor. Math. Phys.**5**(2002) 265-309 [doi:10.4310/ATMP.2001.v5.n2.a3, arXiv:hep-th/0102018]Ilka Brunner, Jacques Distler, Rahul Mahajan,

*Return of the Torsion D-Branes*, Adv. Theor. Math. Phys.**5**(2002) 311-352 [doi:10.4310/ATMP.2001.v5.n2.a4, arXiv:hep-th/0106262]

added pointer to:

- Michael Green, Jeffrey A. Harvey, Gregory Moore,
*I-Brane Inflow and Anomalous Couplings on D-Branes*, Class. Quant. Grav.**14**(1997) 47-52 [arXiv:hep-th/9605033, doi:10.1088/0264-9381/14/1/008]

For when the editing functionality is back, to add some references on the suggestion to use some kind of “holomorphic K-theory” to see D-brane charges on CYs:

Eric R. Sharpe,

*D-Branes, Derived Categories, and Grothendieck Groups*, Nucl. Phys. B**561**(1999) 433-450 (arXiv:hep-th/9902116, doi:10.1016/S0550-3213(99)00535-0)E. G. Scheidegger, Section 5.3.3 in:

*D-branes on Calabi-Yau Spaces*, 2001 (doi:10.5282/edoc.445, pdf)

I have split off a sub-subsection “Twisted, equivariant and differential refinement”, but this still needs more work.

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- Greg Moore,
*K-Theory from a physical perspective*, in: Ulrike Tillmann (ed.)*Topology, Geometry and Quantum Field Theory*, Proceedings of the 2002 Oxford Symposium in Honour of the 60th Birthday of Graeme Segal, Cambridge University Press (2004) (arXiv:hep-th/0304018, doi:10.1017/CBO9780511526398.011)

and added this addendum (here):

see also

- Theodore Erler,
*Four Lectures on Analytic Solutions in Open String Field Theory*(arXiv:1912.00521, spire:1768105)

which still lists (on p. 112) among open problems of string field theory:

“Are there topological invariants of the open string star algebra representing D-brane charges?”

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after mentioning of Witten’s original argument about tachyon condensation, I added this comment (here):

The closest towards an actual check of this second argument about open superstring tachyon condensation (Witten 98, Section 3) seems to be

- Theodore Erler,
*Analytic Solution for Tachyon Condensation in Berkovits’ Open Superstring Field Theory*, JHEP 1311 (2013) 007 (arXiv:1308.4400)

which concludes with:

It would also be interesting to see if these developments can shed light on the long-speculated relation between string field theory and the K-theoretic description of D-brane charge [75, 76, 77]. We leave these questions for future work.

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I have made more explicit (here) the two observations that are the basis for the conjecture; and cross-linked more explicitly with *Sen’s conjecture*

this is a bare list of references, to be `!include`

-ed into relevant entries (such as *D-brane*, *Dirac charge quantization* and *D-brane charge quantization in K-theory*).

In fact, the list is that which has been in each of these entries all along, and it has been a pain to synchronize the parallel lists. So this here now to ease the process.

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